Silane copolymer coatings

ABSTRACT

The invention is drawn to silane copolymers prepared from the reaction of one or more polyisocyanates with one or more lubricious polymers having at least two functional groups, which may be the same or different, that are reactive with an isocyanate functional group and with one or more organo-functional silanes having at least two functional groups, which may be the same or different, that are reactive with an isocyanate functional group and at least one functional group reactive with a silicone rubber substrate. The silane copolymer coatings of the invention are elastic, lubricious, and resist wet abrasion. They are useful as coatings for polysiloxane (rubber) and other difficult to coat substrates, especially for medical devices, such catheters.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.09/189,240, filed Nov. 10, 1998 now U.S. Pat. No. 6,329,488.

FIELD OF THE INVENTION

The invention relates generally to biocompatible, hydrophilic coatings,their manufacture, and their use for coating silicone and otherdifficult to coat medical devices. More specifically, the inventionrelates to hydrophilic coatings which are elastic when dry and resistwet abrasion, and to their use as coatings for polydimethylsiloxane(silicone) rubber substrates.

BACKGROUND OF THE INVENTION

In the practice of medicine there are many diagnostic and therapeuticprocedures which require the insertion of a medical device into thehuman body through an orifice or tissue or contact of a medical devicewith blood or tissue. Such devices include guidewires; catheters,including Foley, angioplasty, diagnostic, and balloon catheters; implantdevices; contact lenses; IUDs; peristaltic pump chambers; endotrachealtubes; gastroenteric feed tubes; arteriovenous shunts; condoms; andoxygenator and kidney membranes. It is necessary for the surface ofthese medical devices to have a low coefficient of friction to preventinjury, irritation, or inflammation to the patient and to facilitatemedical and surgical procedures.

There is a need in the art for medical devices with the appropriatedegree of slipperiness. The appropriate level is one at which the deviceis very slippery when contacted with the patient's moist tissue, but isnot so slippery when dry that it is difficult for medical personnel tohandle. Current materials from which such medical devices are madeinclude silicone rubber, Teflon®, polyethylene (PE), polypropylene (PP),polyvinyl chloride (PVC), polyurethane (PU), polytetrafluoroethylene(PTFE), Nylon®, polyethylene terephthalate (PET), and glass. Thesematerials, however, lack the desired degree of slipperiness.

One approach to providing medical devices with more desirable surfacecharacteristics is to coat the devices made from existing materials withvarious coating compositions. These coatings may be applied by sprayingor painting the coating on the device or by dipping the device in asolution of the coating. Some substances which have been employed ascoatings are Teflon®, silicone fluid, glycerin, mineral oils, olive oil,K-Y jelly, and fluorocarbons. However, these substances have not beenentirely satisfactory because they lack hydrophilicity, are not retainedon the device surface during the period of use, are non-durable, orexhibit inadequate retention of lubricity.

Hydrophilic polymer and hydrogel coatings were an improvement to the artand have been used successfully to provide coatings for many of theeasier to coat substrates, such as polyurethane and latex rubber. Thesecoatings, however, are poorly adherent to silicone rubber and wash offwhen the device is wetted.

Many medical devices such as guidewires, catheters, implant devices,contact lenses, IUDs, peristaltic pump chambers, endotracheal tubes,gastroenteric feed tubes, artenovenous shunts, condoms, and oxygenatorand kidney membranes are made from silicone rubber or other difficult tocoat materials, such as Teflon®, polyethylene and polypropylene. Thus,there is a special need in the art for hydrophilic coatings for theseand similarly difficult to coat substrates.

Adherence of previously known coatings to such surfaces is difficultbecause the coatings do not form covalent bonds with the silicone. As aresult, the coatings have poor adherence, reduced durability, and poorresistance to wet abrasion.

Various polymers have been employed as coatings for medical devices.These include polyethylene oxide (PEO), polyethylene glycol (PEG),polyvinyl pyrrolidone (PVP), and polyurethane (PU). PEO and PEG arefriction-reducing, blood-compatible polymers that are commerciallyavailable in a variety of molecular weights. Both have been used incombination with various other materials to produce lubricious coatingsfor medical devices. For example, coatings incorporating PEO andisocyanates are known in the art (U.S. Pat. Nos. 5,459,317, 4,487,808,and 4,585,666 to Lambert; and U.S. Pat. No. 5,558,900 to Fan et al.). Inaddition, polyols may be incorporated into such PEO/isocyanate coatingsto produce a crosslinked polyurethane (PU) network entrapping the PEO(U.S. Pat. Nos. 5,077,352 and 5,179,174 to Elton). PEO has also beencombined with structural plastic having a high molecular weight toproduce a coating with reduced friction (U.S. Pat. No. 5,041,100 toRowland).

None of these coatings are acceptable for coating silicone rubber andother difficult to coat substrates. Because these coatings do not formcovalent linkages with the silicone surface of the substrate, they havepoor adherence and durability and are easily washed from the surfacewhen the substrate is wetted.

Another polymer used to coat medical devices is polyvinyl pyrrolidone(PVP). PVP may be used as a coating alone or in combination with otherpolymers. For example, polyvinyl pyrrolidone may be bonded to asubstrate by thermally activated free radical initiators, UV lightactivated free-radical initiators, or E-beam radiation (WO 89/09246).One disadvantage of using such coatings is that E-beam radiation can bedeleterious to some of the materials used in medical devices.

PVP may be used in conjunction with other polymers. One such coating ismade from PVP and glycidyl acrylate. This coating requires the presenceof amino groups on the surface of the substrate to react with the epoxygroups of the glycidyl acrylate to covalently bond the PVP-containingcopolymer to the substrate (Nagoacha et al, Biomaterials, 419 (1990)).Silicone rubber does not contain any free amino groups, and thus thistype of coating cannot form covalent bonds with the surface of thesilicone substrate, resulting in poor adhesion.

Other coatings are composed of a mixture of PVP and polyurethane. Thesecoatings provide low friction surfaces when wet. One such coating is apolyvinyl pyrrolidone-polyurethane interpolymer (U.S. Pat. Nos.4,100,309 and 4,119,094 to Micklus et al.). Another such coating iscomposed of hydrophilic blends of polyvinyl pyrrolidone (PVP) and linearpreformed polyurethanes (U.S. Pat. No. 4,642,267 to Cresy). In addition,PVP may be incorporated into a PU network by combining a polyisocyanateand a polyol with a PVP solution (U.S. Pat. Nos. 5,160,790 and 5,290,585to Elton). Still another such coating is composed of two layers: aprimer and a top coat. The primer coat is a polyurethane prepolymercontaining free isocyanate groups, while the top coat is a hydrophiliccopolymer of PVP and a polymer having active hydrogen groups, such asacrylamide (U.S. Pat. No. 4,373,009 to Winn).

None of these PVP based coatings are acceptable for coating siliconerubber and other difficult to coat substrates. Because these coatings donot form covalent linkages with the silicone surface of the substrate,they have poor adherence and durability and are easily washed from thesurface when the substrate is wetted.

Hydrophilic polyurethanes have also been used in formulations other thanwith PVP as coatings for medical devices. For example, the prior artdiscloses coatings composed of polyurethane hydrogels containing arandom mixture of polyisocyanates and a polyether dispersed in anaqueous liquid phase (U.S. Pat. No. 4,118,354 to Harada et al.).Polyurethanes have also been used as coatings in compositions containingchain-extended hydrophilic thermoplastic polyurethane polymers with avariety of hydrophilic high molecular weight non-urethane polymers (U.S.Pat. No. 4,990,357 to Karkelle et al.). It is also known to mix urethanewith a silicone or siloxane emulsion. The carboxylic acid groups of thesubstrate and coating may then be linked with a cross-linking agent,such as a polyfunctional aziridine (U.S. Pat. No. 5,026,607 toKiezulas).

Because the urethane and non-urethane polymers cannot react with oneanother or the surface to be coated, the resulting coatings have pooradhesion, especially to silicone surfaces. Also, since silicone surfacesdo not contain free carboxylic acid groups, a crosslinker such as apolyfunctional aziridine will not covalently bond known coatings to thesurface of a silicone substrate.

Thus, there is a critical need in the art for an improved coating whichis not slippery when dry but becomes slippery when contacted withaqueous fluids and which will adhere to medical devices made fromsilicone and other difficult to coat materials.

There is also a need in the art for a coating having improved durabilityand uniformity which retains its lubricity and will adhere to medicaldevices made from silicone and other difficult to coat materials.

There is also a need in the art coatings which are biocompatible andabrasion resistant, having a low wet coefficient of friction, that willadhere to medical devices made from silicone and other difficult to coatmaterials.

There is a further need in the art for a process of preparing lubriciouscoatings for medical devices made from silicone and other difficult tocoat materials which is simple and efficient and results in uniformitybetween batches.

SUMMARY OF THE INVENTION

Stated generally, the present invention comprises biocompatible,hydrophilic silane copolymers, their manufacture, and their use ascoatings for polydimethylsiloxane rubber and other difficult to coatsubstrates. The coatings of the invention provide advantageousproperties, such as improved durability, uniformity, and adhesion tosilicone and other surfaces which are difficult to coat, such aspolyethylene and polypropylene. The coatings of the present inventionare beneficial because they retain lubricity and do not leachexcessively over time.

Stated somewhat more specifically, the invention in a first aspectcomprises a method for preparing a silane copolymer from one or morepolyisocyanates, from one or more lubricious polymers having at leasttwo functional groups, which may be the same or different, that arereactive with an isocyanate functional group, and from one or moreorgano-functional silanes having at least two functional groups, whichmay be the same or different, that are reactive with an isocyanatefunctional group and at least one functional group reactive with asilicone rubber substrate. The invention also comprsises the silanecopolymers made from the process described above.

In another aspect, the present invention comprises using the silanecopolymers described herein to coat polysiloxane rubber and otherdifficult to coat substrates. The coatings may comprise either a singlelayer or multiple layers. In one preferred embodiment, the copolymers ofthe invention are employed as a primer coat over which a top coat isapplied. In s another preferred embodiment, the coating is applied asthe sole coating to the catheter. In yet another preferred embodiment,the copolymer coating incorporates additional components, includingother hydrophilic polymers. Also included in the invention are thecoatings formed from the silane copolymers and the articles containingsuch coatings.

Thus, it is an object of the present invention to provide an improvedcoating for silicone and other difficult to coat substrates which is notslippery when dry but becomes slippery when contacted with aqueousfluids.

It is another object of the invention to provide a coating with improveddurability and uniformity which retains its lubricity.

Further, it is an object of the present invention to provide a coatingwith improved adhesion to silicone and other surfaces that are difficultto coat.

Additionally, it is an object of the invention to provide a coatingwhich does not leach over time.

It is an object of the invention to provide coatings which arebiocompatible and abrasion resistant, having a low coefficient offriction.

It is another object of the present invention to provide a single layer,lubricious coating.

It is yet another object of the invention to provide a multi-layercoating which comprises a primer coating layer and a lubricious topcoat.

It is an object of the invention to provide a polyurethane-silanecopolymer.

It is another object of the present invention to provide apolyurethane-urea-silane copolymer.

It is a further object of the present invention to provide a process ofpreparing lubricious coatings which is simple and efficient and resultsin uniformity between batches.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It should be understood to those well versed in the art of polymer andpolyurethane synthesis that the copolymer coatings of the presentinvention may take many different forms and may be made by manydifferent methods, and that the disclosure of the preferred embodimentsherein do not limit the scope of the invention.

Preparing the Silane Copolymers of the Invention

Generally the present invention comprises a process for preparing silanecopolymers. Stated somewhat more specifically, the invention in a firstaspect comprises a method for preparing a silane copolymer from one ormore polyisocyanates, from one or more lubricious polymers having atleast two functional groups, which may be the same or different, thatare reactive with an isocyanate functional group, and from one or moreorgano-functional silanes having at least two functional groups, whichmay be the same or different, that are reactive with an isocyanatefunctional group and at least one functional group reactive with asilicone rubber substrate.

The process of the invention may be performed in many variations. Forexample, the silane copolymers of the present invention can be preparedby first forming a prepolymer from the polyisocyanate(s) and lubriciouspolymer(s) followed by reaction with the organo-functional silane(s).Alternatively, the silane copolymers of the invention can be prepared byfirst forming a prepolymer from the polyisocyanate(s) and silane(s)followed by reaction with the lubricious polymer(s). Additionally, thesilane copolymers of the invention can be prepared by simultaneouslyadding the polyisocyanate(s), lubricious polymer(s), and silane(s) andallowing them to react with one another to form the copolymer of theinvention.

While any monomers satisfying the definition above may be employed inthe invention, for convenience, the process of invention will bedescribed further in terms of the production of polyurethane-urea-silanecopolymers. However, it should be understood that these specificcopolymers are only preferred embodiments and in no way limit the scopeof the invention.

In one disclosed embodiment, one or more polyols are reacted with anexcess of one or more polyisocyanates in the presence of a catalyst,such as a tin catalyst. The polyurethane product of this first step isthen reacted with one or more amino-functional alkoxysilanes to form apolyurethane-urea-silane copolymer having pendant alkoxy groups. Thispolyurethane-urea-silane copolymer is then optionally stabilized insolution by the addition of an alcohol, preferably the alcohol formed bythe reaction of the alkoxy group with water.

In a preferred form of the embodiment, one or more polyols are reactedwith an excess of a diisocyanate in a first step to form anisocyanate-capped polyurethane prepolymer. The formation of thisprepolymer can be facilitated by employing an excess of polyisocyanate.In other words, the number of isocyanate functional groups present inthe reaction mixture is greater than the number of alcohol functiongroups present in the reaction mixture. Preferably, the ratio ofisocyanate functional groups to alcohol or other isocyanate reactivefunctional groups is from 1.1:1 to 2:1. More preferably, the ratio ofisocyanate functional groups to alcohol functional groups is from 1.5:1to 2:1, most preferably 1.6 to 1.8.

The reaction between the polyol and polyisocyanate can also befacilitated by employing a catalyst. Nonlimiting examples of suitablecatalysts are tertiary amines, such as N,N-dimethylaminoethanolN,N-dimethyl-cyclohexamine-bis(2-dimethyl aminoethyl) ether,N-ethylmorpholine, N,N,N′,N′,N″-pentamethyl-diethylene-triamine, and1-2(hydroxypropyl) imidazole, and metallic catalysts, such as tin,stannous octoate, dibutyl tin dilaurate, dioctyl tin dilaurate, dibutyltin mercaptide, ferric acetylacetonate, lead octoate, and dibutyl tindiricinoleate. The preferred catalyst is tin. The most preferredcatalyst is dioctyl tin dilaurate.

In a second step, the isocyanate-capped polyurethane-urea prepolymer isreacted with an organo-functional silane to form apolyurethane-urea-silane copolymer having pendant alkoxy groups. Anyorgano-functional silane having at least two functional groups, whichmay be the same or different, that are reactive with an isocyanatefunctional group, and at least one functional group reactive with asilicone surface may be used in the process of the present invention.The reaction can be facilitated by performing the polymerization in adry organic solvent. If the silicone reactive group of the silane isalkoxy, an optional third step comprises stabilization of the alkoxygroups of the polyurethane-urea-silane copolymer by the addition analcohol of the alcohol corresponding to the reaction product of thealkoxy group with water.

In a second disclosed embodiment, one or more amino-functionalalkoxysilanes are reacted with an excess of one or more polyisocyanates,preferably a diisocyanate. The polyurea product of this first step isthen combined with one or more polyols, optionally in the presence of acatalyst, such as a tin catalyst. If a catalyst is used, apolyurethane-urea-silane copolymer having pendant alkoxy groups. Thispolyurethane-urea-silane copolymer is then optionally stabilized insolution by addition of the alcohol corresponding to the alcohol formedby the reaction of the alkoxy group with water.

In a third disclosed embodiment of the process, one or moreamino-functional alkoxysilanes are reacted with one or morepolyisocyanates, preferably a diisocyanate, and one or more polyols,optionally in the presence of a catalyst, such as a tin catalyst, toform a polyurethane-urea-silane copolymer having pendant alkoxy groups.This polyurethane-urea-silane copolymer is then optionally stabilized insolution by addition of the alcohol corresponding to the alcohol formedby the reaction of the alkoxy group with water.

When alokysilanes are used in the present invention, the resultingpolyurethane-urea-silane copolymers contain numerous free alkoxy groupswhich react with the silicone surface but can also react with any waterpresent in the reaction system. The reaction of the alkoxy groups withwater cleaves alcohol from the copolymer and leaves silanol groups inplace of the alkoxy groups. These silanols may react with the siliconesubstrate or with each other, the latter producing crosslinks in thecopolymer which can affect coating properties.

Addition to the copolymer solution of the alcohol formed by the reactionof the alkoxy group contained in the copolymer and water helps tostabilize the copolymer by inhibiting the reaction of alkoxy groups withwater. Examples of such alcohols include, but are not limited to,methanol, ethanol, 1-propanol, 2-propanol, butanol, hexanol and octanol.The particular alcohol used will depend upon the alkyl portion of thealkoxy group. For example, methanol is used to stabilize a copolymercontaining methoxy groups. The alcohol is generally added at the end ofpolymerization in an amount from 5 to 50% of the total solventcomposition, preferably from 10 to 30%.

Any polyol may be used in the process of the invention and is preferablydried to less than 1000 ppm water before reaction. Examples of suchpolyols include, but are not limited to, polyethylene glycols, polyesterpolyols, polyether polyols, caster oil polyols, and polyacrylatepolyols, including Desmophen A450, Desmophen A365, and Desmophen A160(Mobay Corporation, Pittsburgh, Pa.).

The process advantageously employs a diol as the polyol. Suitable diolsinclude, but are not limited to, poly(ethylene adipates),poly(diethyleneglycol adipates), polycaprolactone diols,polycaprolactone-polyadipate copolymer diols,poly(ethylene-terephthalate)diols, polycarbonate diols,polytetramethylene ether glycol, polyethylene glycol, ethylene oxideadducts of polyoxypropylene diols, ethylene oxide adducts ofpolyoxypropylene triols. The preferred polyol is the diol polyethyleneglycol. The most preferred polyethylene glycol is CARBOWAX 1450(available from Union Carbide).

Instead of polyols, amine functional polymers may be used in the processof the invention to produce isocyanate-functionalized polyureas forreaction with an amino-functional alkoxysilane. Additionally, aminefunctional chain extenders common to the art of polyurethane synthesisand water which also produces polyureas by reaction with isocyanates toproduce amines, may also be employed. Monomers containing such chainextenders also produce polyureas. Replacement of polyols with otherpolymers having functional groups reactive with isocyanates, as well asthe use of other common polyurethane/polyurea synthetic techniques knownto the art are anticipated by the process of the present invention.

Any polyisocyanate may be used in the process of the present invention.The polyisocyanate may be aromatic, aliphatic or cycloaliphatic.Nonlimiting examples of such polyisocyanates are 4,4′-diphenylmethanediisocyanate and position isomers thereof, 2,4- and 2,6-toluenediisocyanate (TDI) and position isomers thereof, 3,4-dichlorophenyldiisocyanate, dicyclohexylmethane-4,4′-diisocyanate (HMDI),4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylene diisocyanate(HDI) and position isomers thereof, isophorone diisocyanate (IPDI), andadducts of diisocyanates, such as the adduct of trimethylolpropane anddiphenylmethane diisocyanate or toluene diisocyanate. The preferredpolyisocyanate is the diisocyanate dicyclohexylmethane-4,4′-diisocyanate(HMDI).

Any organo-functional silanes having at least two functional groups,which may be the same or different, that are reactive with an isocyanatefunctional group and at least one functional group reactive with asilicone surface may be used in the process of the present invention.Nonlimiting examples of organo-functional silanes areN-beta-(aminoethyl)-gamma-aminopropyl-trimethoxy silane andN-(2-aminoethyl)-3-aminopropylmethyl-dimethoxy silane. The preferredorgano-functional silane is a diamino-alkoxysilane, such asN-(2-aminoethyl)-3-aminopropylmethyldimethoxy silane.

In general, it is beneficial to add a catalyst to the isocyanatereaction mixtures. Although any catalyst known to be useful inisocyanate reactions may be employed, the preferred catalyst for thepresent invention is any tertiary amine or metallic catalyst.Nonlimiting examples of suitable catalysts include tertiary amines, suchas N,N-dimethylaminoethanol, N,N-dimethyl-cyclohexamine-bis(2-dimethylaminoethyl) ether, N-ethylmorpholine,N,N,N′,N′,N″-pentamethyl-diethylene-triamine, and 1-2(hydroxypropyl)imidazole, and metallic catalysts, such as tin, stannous octoate,dibutyl tin dilaurate, dioctyl tin dilaurate, dibutyl tin mercaptide,ferric acetylacetonate, lead octoate, and dibutyl tin diricinoleate. Thepreferred catalyst is tin with the most preferred being dioctyl tindilaurate.

A solvent is advantageously added to the prepolymer or monomer mixtureto reduce viscosity. The level of viscosity is important during thesynthesis of the copolymers of the present invention. Duringpolymerization, if the copolymer solution attains too high a viscosity,the solution can form a gel from which good quality coatings cannot bemade. Once the polymerization is complete, if the copolymer solution hastoo high a viscosity, the coating formed will be too thick to produce auniform thin coating on the substrate. Such a coating may also have lowdurability due to cracking. On the other hand, if copolymer solution hastoo low a viscosity, the coating formed will exhibit poor and unevenadhesion.

Viscosity is a function of molecular weight of the copolymer and thesolids content of the solution and is controlled by addition of solventto the solution. The preferred copolymer solution for dip coating has akinematic viscosity in a range of about 1.5 to 20 cS (centistokes),preferably 2.0 to 10 cS, and most preferably 2.5 to 5 cS. The preferredcopolymer solution has a solids content in a range of about 0.4 to 5%,most preferably from 0.6 to 1.5%.

It is preferred but not essential that the solvent be dry to preventwater contamination of the prepolymer because water may react withalkoxy groups of the silane. The solvent preferably contains less than200 ppm water. Solvents which are useful in the present inventioninclude, but are not limited to, tetrahydrofuran, acetonitrile, ethylacetate, methylene chloride, dibromomethane, chloroform, dichloroethane,and dichloroethylene, with tetrahydrofuran being preferred.

The Silane Copolymers of the Invention

In a second aspect, the present invention comprises the silanecopolymers made by the processes described above. These copolymers arepreferably polyurethane-urea-silane copolymers. Particularly preferredcopolymers are polyurethane-urea-silane copolymers having from 7 to 12%by weight silane based upon the weight of the entire copolymer. The mostpreferred copolymers of the invention are those comprised ofdicyclohexylmethane-4,4′-diisocyanate,N-(2-aminoethyl)-3-aminopropylmethyldimethoxy silane, and CARBOWAX 1450.

The silane copolymers can contain additional components. For example,they may contain viscosity and flow control agents, antioxidants,conventional pigments, air release agents or defoamers, and otherhydrophilic polymers.

Antioxidants are not necessary, but may be used to improve the oxidativestability of the coatings. Nonlimiting examples of useful antioxidantsare vitamin E, tris(3,5-di-t-butyl-4-hydroxy benzyl) isocyanurate,2,2′-methylenebis(4-methyl-6-t-butyl phenol),1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxy benzyl) benzene,butyl-hydroxytoluene, octadecyl-3,5-di-t-butyl-4-hydroxy hydrocinnamate,4,4′-methylenebis(2,6-di-t-butylphenol), p,p′-dioctyl-diphenylamine, and1,1,3-tris-(2-methyl-4-hydroxy-5-t-butylphenyl)butane.

Conventional dyes and pigments can be added to impart color orradiopacity or to enhance the aesthetic appearance of the coatingsproduced from the copolymers.

The Use of the Copolymers as Lubricious Coatings

In a third aspect, the present invention comprises a method for usingthe silane copolymers described above to form a lubricious coating ondifficult to coat substrates. Although the preferred substrate is apolysiloxane rubber, the copolymer is also useful for coating otherdifficult to coat substrates, such as polyethylene and polypropylene, aswell as other polymers, glass, metal, and ceramics. Many medicaldevices, such as guide wires; catheters, including Foley, angioplasty,diagnostic, and balloon catheters; implant devices; contact lenses;IUDs; peristaltic pump chambers; endotracheal tubes; gastroenteric feedtubes; arteriovenous shunts; condoms; and oxygenator and kidneymembranes, are made from silicone rubber and these other substrates.

The silane copolymers of the invention may be applied to the substrateby conventional methods known in the art. In general, the substrate isdipped into a solution of the copolymer of the present invention.Preferably, the substrate is dipped into the copolymer solution at arate of about 15-80 inches per minute (ipm), preferably about 40 ipm.The substrate is preferably allowed to remain in the coating solutionfor 0-30 seconds, preferably about 5-15 seconds, and then is withdrawnat a rate of about 10-80 ipm, preferably 15-30 ipm. Once the substratehas been coated with the copolymer of the invention, it is allowed toair dry for at least 1 hour. The substrate may optionally be dried witha hot air stream or in an oven at a temperature of approximately 50 to100° C. for about 5-60 minutes to remove residual solvent.

The silane copolymers of the present invention can be used to form avariety of unique coatings by varying the exact components incorporatedinto the copolymer. Some of the copolymers are both very lubricious andadhesive to the substrate. These copolymers can be used as the solecoating on the substrate. Other of the copolymers of the invention areless lubricious but have superior adhesion. These copolymers can be usedas a primer coat over which a lubricious top coat may be attached.

In a first disclosed embodiment, the silane copolymer of the inventionmay be applied to the substrate as a primer coat over which a secondlubricious top coat is then applied. In this embodiment, the silanecopolymer acts as a primer, facilitating adhesion of the second top coatto the substrate. The top coat may be applied by any method, but isadvantageously applied by dipping the primed substrate into a solutionof the top coat in a manner similar to that by which the primer isapplied.

As mentioned above, the preferred polyol used in the preparation of thesilane copolymer is polyethylene glycol (PEG). PEG is a polymeric diolwhich is available in a variety of molecular weights. The use of PEGhaving different molecular weights affects the molecular weight andlubricity of the coatings formed. When the silane copolymer is used as aprimer coat, a PEG having a lower molecular weight, such asCARBOWAX_(—)1450, is used. The use of CARBOWAX 1450 provides aprepolymer having a weight average molecular weight (M_(w)) that isgenerally between about 1,900 and 25,000 as measure by gel permeationchromatography (GPC). A copolymer made from such a prepolymer providesimproved adhesion of the primer coat to the substrate.

The lubricious top coat may be any coating which enhances the lubricityof the substrate. One preferred top coat is the combination of a highermolecular weight polyethylene oxide, such as Hydroslide 121 (C.R. Bard,Inc., Murray Hill, N.J.) or a polyvinyl pyrrolidone and a reactivemixture of polyfunctional isocyanate and polyol. Examples of such topcoats include the coatings disclosed in U.S. Pat. Nos. 5,077,352;5,179,174; 5,160,790; and 5,209,585, herein incorporated by reference.

Alternatively, the lubricious top coat that is applied over the primercoat is the silane copolymer of the present invention made with a highermolecular weight PEG, such as CARBOWAX 8000. Copolymers made from ahigher molecular weight PEG, such as CARBOWAX 8000, exhibit an increasedlubricity over copolymers made with a lower molecular weight PEG such asthat used in the primer coat.

In a second disclosed embodiment, the silane copolymers of the inventionmay be applied to the substrate as a single coating when a sufficientlylubricious polyol, such as CARBOWAX 8000, is incorporated into thecopolymer. The copolymers of the invention may be used alone as thesingle coating, or may incorporate additional hydrophilic polymers intothe copolymer to add desirable properties to the coating. The preferredcopolymers of this embodiment contain at least one additionalhydrophilic polymer, such as polyethylene glycol (PEG), polyethyleneoxide (PEG), or polyvinyl pyrrolidone (PVP).

Hydrophilic polymers that may be added to the copolymer solutioninclude, but are not limited to, polyethylene oxide (PEO), polyethyleneglycol (PEG), polysaccharides, hyaluronic acid and its salts andderivatives, sodium alginate, chondroitin sulfate, celluloses, chitin,chitosan, agarose, xanthans, dermatan sulfate, keratin sulfate, emulsan,gellan, curdlan, amylose, carrageenans, amylopectin, dextrans, glycogen,starch, heparin sulfate, and limit dextrins and fragments thereof;synthetic hydrophilic polymers, poly(vinyl alcohol), and poly(N-vinyl)pyrrolidone (PVP). The preferred hydrophilic polymer for use in thepresent invention is polyethylene glycol.

Properties of Lubricious Coatings of the Invention

The lubricious coatings made by this process have a number ofadvantageous properties. These properties include a reduced coefficientof friction when wet, providing a very slippery surface, increasedcoating adhesion to silicone and other difficult to coat substrates, andincreased coating durability on such substrates.

Coefficient of friction (COF) is a measure of how slippery the coatingis when contacted with another surface, such as body tissue. The lowerthe COF, the more slippery is the coating. Medical devices whosesurfaces become slippery when wet decrease patient discomfort anddecrease trauma to the patient's tissue. It is, therefore, desirable toproduce a coating having as low of a COF as possible when wet. Thecoatings of the present invention have a COF when wet of between 0.01and 0.2, preferably between 0.01 and 0.12, and more preferably between0.01 and 0.06. In contrast, uncoated surfaces of most medical devicestypically have wet COFs greater than 0.35. Thus, coatings of the presentinvention are excellent for use on the surface of medical devices,especially those made of silicone and other difficult to coat surfacesbecause they reduce the COF of the surfaces.

Coating adhesion and durability are both affected by the copolymer'smolecular weight. The molecular weight in turn is dependent upon anumber of factors: (1) the amount of water initially present in thepolyol, (2) the final prepolymer molecular weight, (3) the prepolymerisocyanate functionality, (4) how close the ratio of prepolymerisocyanate groups to amine groups in the organo-functional silaneapproaches a 1:1 stoichiometric ratio, (5) purity of the silane monomer,(6) the water content of the solvents used, and (7) the degree ofviscosity the copolymer is allowed to attain before the final dilution.

An important factor which contributes to both the copolymer molecularweight and the reproducibility of the copolymer synthesis is watercontamination. Water can affect the copolymer molecular weight and thereproducibility of the copolymer synthesis in several ways. First,because water reacts with isocyanate groups to form primary amines, itcan affect the stoichiometry of the polymerization. Second, water canreact with the methoxy groups of DAS to form crosslinks within thecopolymer, which dramatically increase the molecular weight of thecopolymer. Therefore, it is desirable to limit the amount of waterpresent during manufacture of the coating. Some of the ways to limitwater contamination are the use of molecular sieves, vacuum drying,anhydrous reactants and a dry, inert atmosphere. If polyethylene glycolor other hygroscopic starting material is used in the copolymersynthesis, it is preferred that it be adequately dried to a consistentmoisture level before use. Hygroscopic materials such as polyethyleneglycol can absorb significant quantities of water from the air in ashort period of time.

The ratio of isocyanate groups on the prepolymer to amine groups on theorgano-functional silane also affects the molecular weight of thecopolymer. A 1:1 ratio produces a copolymer approaching infinitemolecular weight. The number of free isocyanate groups present in theprepolymer limits the number of sites available for reaction with theamine groups on the organo-functional silane. Similarly, the purity ofthe silane affects the number of amine groups available for reaction.

This invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations upon thescope of the invention.

EXPERIMENTAL DATA Example 1

Preparation of Polyethylene Glycol

To a glass jar was added 200 g of polyethylene glycol (PEG) 1450 (UnionCarbide) followed by the addition of 50 g molecular sieves. The jar wasthen placed in a vacuum oven at 68° C. for 72 hours under full vacuum.The water content of the PEG was then analyzed by Karl Fischer titrationand determined to be 454 ppm.

Example 2

Preparation of Urethane Prepolymer

A three neck 300 ml round bottom flask was equipped with an overheadstirrer, a nitrogen inlet, and a nitrogen bubbler. The flask was placedin a 70° C. oil bath. The nitrogen bubbler was removed and 11.60 gdried, molten PEG 1450 was injected into the flask with a syringe. Tothe molten PEG was added 4.03 g of Desmodur W (Bayer, Inc. Germany) bysyringe. The flask was then flushed with nitrogen, and a nitrogenblanket was maintained over the reaction mixture throughout theprocedure.

The reaction mixture was stirred until homogenous. Next, 0.015 g ofdioctyl tin dilaurate was added to the reaction mixture with a syringe.The mixture was then stirred for 1.2 hours at 68° C. to form theurethane prepolymer.

Example 3

Synthesis of polurethane-urea-silane copolymer primer

A three-neck, 500 ml, round bottom flask was set up with an overheadstirrer, addition funnel with nitrogen inlet, and septum seal withnitrogen bubbler (outlet). The system was flushed with nitrogen. 111.5 gof dry (less than 100 ppm water) tetrahydrofuran (THF) was added to theurethane prepolymer prepared in Example 2, and the mixture was stirreduntil homogenous.

Next, 1.53 g of N-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane(DAS) (Gelest, Inc.) was dissolved in 38.63 g THF and added continuouslyto the prepolymer solution via the addition funnel over a period ofapproximately five minutes to begin the polymerization. The solidsconcentration of the solution was approximately 10% at this point.

The viscosity of the mixture was monitored, and when it increased to70.9 centipoise (cP), 48.3 g of anhydrous THF was added. The viscosityfell and then began building again. When it reached 70.0 cP again, 49.33g of anhydrous THF was added. This process was repeated, adding another48.62 g of anhydrous THF when 67.6 cP was reached. When the viscosityreached the fourth target of 66.0 cP, 30.16 g of THF was added toproduce a 5% solids solution. When the viscosity reached a finalviscosity of 67.1 cP, the solution was transferred into a 2 L vesselcontaining 690 g of THF and stirred until homogeneous. 354.3 g ofmethanol was then added to stabilize the silane copolymer, producing afinal solution concentration of 1.2% solids. The amount of methanol inthe solvent mixture was sufficient to produce a final methanolconcentration of 25% of the total solvent. The copolymer solution wasthen diluted to 0.81% solids with a solution of 75% THF and 25% methanolto produce a final viscosity of 4.02 cS.

Example 4

Preparation of Hydroslide 121 Polyurethane Hydrogel

3.42 g of Polyox N750 (Union Carbide) was dissolved in 580.6 gdichloromethane. 1.09 g Polycin 12 (Caschem, Inc.) was then added to thePolyox solution and stirred until homogenous. Then, 0.96 g DesmodurCB60N (Bayer, Inc., Germany) was added to the solution and mixed untilhomogenous.

Example 5

Thirty catheters were dipped into the primer copolymer solution ofExample 3 at a rate of about 41.2 ipm. The catheters were allowed toremain in the coating solution for 10 seconds and then withdrawn at arate of about 14.9 ipm. The catheters were air dried by passing a gentlestream of air through the drainage lumen of the catheters for about 5minutes, followed by air drying for one hour.

Example 6

15 the thirty catheters from Example 5 were then dipped into a solutionof the Hydroslide 121 coating prepared in Example 4 at a rate of 41.1ipm and withdrawn at a rate of 15.2 ipm. The catheters were then airdried by passing a gentle stream of air through the drainage lumen forabout 5 minutes, air drying them for an additional 30 minutes, and thenplacing them into an oven at 80° C. for 15 minutes. The catheters wereallowed to cool and then packaged and sterilized with ethylene oxide(ETO). After sterilization, the coefficient of friction of 10 pairs ofthe silicone copolymer coated catheters was evaluated over a 21 dayperiod in which the catheters were incubated in water at 37° C. Whencompared with the coefficient of friction of uncoated siliconecatheters, the results confirmed a highly lubricious, durablehydrophilic coating on the silicone catheters.

Coated? 1 Day 7 Day 14 Day 21 Day YES 0.023 0.026 0.032 0.048 NO 0.2160.237 0.160 0.183

Finally, it will be understood that the preferred embodiments have beendisclosed by way of example, and that other modifications may occur tothose skilled in the art without separating from the scope and spirit ofthe appended claims.

1. An article comprising a polysiloxane rubber substrate having asurface coated with a coating wherein the coating comprises a copolymerthat is the reaction product of molecules comprising: i) one or moremolecules having at least two functional groups, which may be the sameor different, that are reactive with isocyanate; ii) one or moreorgano-functional silanes having at least two functional groups that arereactive with an isocyanate group and at least one functional groupreactive with a silicone rubber substrate; and, iii) one or morepolyisocyanates.
 2. The article of claim 1, wherein the article is amedical device.
 3. The article of claim 1, wherein the article is acatheter.
 4. An article according to claim 1, wherein the one or moreorgano-functional silanes comprise an amino-functional alkoxysilane. 5.The article of claim 4, wherein the amino-alkoxy silane isN-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane.
 6. The article ofclaim 1, wherein the one or more molecules having at least twofunctional groups, which may be the same or different, that are reactivewith isacyanates comprise a diol.
 7. The article of claim 6, wherein thediol is a polyethylene adipate, a polydiethyleneglycol adipate, apolycaprolactone diol, a polycaprolactone-polyadipate copolymer diol, apolyethylene-terephthalate diol, a polycarbonate diol, apolytetramethylene ether glycol, a polyethylene glycol, an ethyleneoxide adduct of a polyoxypropylene diol or an ethylene oxide adduct of apolyoxypropylene triol.
 8. The article of claim 7, wherein thepolyethylene glycol has a weight average molecular weight of about 1450.9. The article of claim 7, wherein the polyethylene glycol has a weightaverage molecular weight of about
 8000. 10. The article of claim 1,wherein the one or more polyisocyanates comprise a diisocyanate.
 11. Thearticle of claim 1, wherein the one or more polyisocyanates comprise4,4′-diphenylmethane diisocyanate or a position isomer thereof, 2,4- or2,6-toluene diisocyanate (TDI) or a position isomer thereof,3,4-dichlorophenyl diisocyanate, dicyclohexylmethane-4,4′-diisocyanate(HMDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylenediisocyanate (HDI) or a position isomer thereof, isophorone diisocyanate(IPDI) or an adduct of a diisocyanate.
 12. The article of to claim 10,wherein the diisocyanate is dicyclohexylmethane-4,4′-diisocyanate(HMDI).
 13. The article of claim 1, wherein the silane copolymer is apolyurethane-urea-silane copolymer.
 14. The article of claim 1, wherein7-12% by weight of the copolymer is the silane based upon the weight ofthe entire copolymer.
 15. The article of claim 1, wherein the coatingfurther comprises a hydrophilic polymer.
 16. The article of claim 15,wherein the hydrophilic polymer is a polysaccharide, hyaluronic acid ora salt or a derivative thereof, sodium alginate, chondroitin sulfate, acellulose, chitin, chitosan, agarose, a xanthan, dermatan sulfate,keratin sulfate, emulsan, gellan, curdlan, amylose, carrageenan,amylopectin, a dextran, glycogen, starch, heparin sulfate, a limitdextrin or a fragment thereof or a synthetic hydrophilic polymer. 17.The article of claim 15, wherein the hydrophilic polymer is polyethyleneoxide (PEO), polyethylene glycol (PEG), poly(vinyl alcohol) orpoly(N-vinyl) pyrrolidone (PVP).
 18. The article of claim 1, wherein theone or more polyisocyanates comprisedicyclohexylmethane-4,4′-diisocyanate (HMDI), the one or moreorgano-functional silanes compriseN-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane, and the moleculeshaving at least two functional groups, which may be the same ordifferent, that are reactive with isocyanate comprise a polyethyleneglycol having a weight average molecular weight of about
 1450. 19. Thearticle of claim 1, wherein the coating comprises a primer coat and atop coat wherein: the primer coat comprises the copolymer and the primercoat is located between the surface and the top coat.
 20. The article ofclaim 19, wherein the top coat comprises polyethylene oxide and areactive mixture of a polyfunctional isocyanate and a polyol.
 21. Thearticle of claim 19, wherein the top coat comprises polyvinylpyrrolidone and a reactive mixture of a polyfunctional isocyanate and apolyol.
 22. The article of claim 19, wherein the top coat is formed byreacting: (i) one or more polyisocyanates, (ii) one or moreorgano-functional silanes having at least two functional groups, whichmay be the same or different and which are reactive with an isocyanategroup, and at least one functional group reactive with a silicone rubbersubstrate, and (iii) a polyethylene glycol.
 23. The article of claim 22,wherein the polyethylene glycol used to form the top coat has a weightaverage molecular weight of about
 8000. 24. The article of claim 1,wherein the coating has a coefficient of friction when wet of between0.01 and 0.2.
 25. The article of claim 1, wherein the coating has acoefficient of friction when wet of between 0.01 and 0.12.
 26. Thearticle of claim 1, wherein the coating has a coefficient of frictionwhen wet of between 0.01 and 0.06.
 27. The article of claim 1, whereinthe molecule having at least two functional groups, which may be thesame or different, that are reactive with an isocyanate functionalgroup, has at least two amino functional groups.
 28. A silane copolymerthat is the reaction product of molecules consisting essentially of: i)a polymer having at least two functional groups, which may be the sameor different, that are reactive with isocyanate; ii) one or moreorgano-functional silanes having at least two functional groups that arereactive with an isocyanate group and at least one functional group thatis reactive with a silicone rubber substrate; and, iii) one or morepolyisocyanates.
 29. The silane copolymer of claim 28, wherein the oneor more organo-functional silanes comprise an amino-functionalalkoxysilane.
 30. The silane copolymer of claim 29, wherein theamino-alkoxy silane is N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane.
 31. The silane copolymer of claim 28, wherein the polymer havingat least two functional groups, which may be the same or different, thatare reactive with isocyanates is a diol.
 32. The silane copolymer ofclaim 31, wherein the diol is a polyethylene adipate, apolydiethyleneglycol adipate, a polycaprolactone diol, apolycaprolactone-polyadipate copolymer diol, apolyethylene-terephthalate diol, a polycarbonate diol, apolytetramethylene ether glycol, a polyethylene glycol, an ethyleneoxide adduct of a polyoxypropylene diol or an ethylene oxide adduct of apolyoxypropylene triol.
 33. The silane copolymer of claim 31, whereinthe diol is a polyethylene glycol.
 34. The silane copolymer of claim 33,wherein the polyethylene glycol has a weight average molecular weight ofabout
 1450. 35. The silane copolymer of claim 33, wherein thepolyethylene glycol has a weight average molecular weight of about 8000.36. The silane copolymer of claim 28, wherein the one or morepolyisocyanates comprise a diisocyanate.
 37. The silane copolymer ofclaim 28, wherein the one or more polyisocyanates comprise4,4′-diphenylmethane diisocyanate or a position isomer thereof, 2,4- or2,6-toluene diisocyanate (TDI) or a position isomer thereof,3,4-dichlorophenyl diisocyanate, dicyclohexylmethane-4,4′-diisocyanate(HMDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylenediisocyanate (HDI) or a position isomer thereof, isophorone diisocyanate(IPDI) or an adduct of a diisocyanate.
 38. The silane copolymer of claim28, wherein the diisocyanate is dicyclohexylmethane-4,4′-diisocyanate(HMDI).
 39. The silane copolyrner of claim 28, wherein the silanecopolymer is a polyurethane-urea-silane copolymer.
 40. The silanecopolymer of claim 28, wherein 7-12% by weight of the copolymer is thesilane based upon the weight of the entire copolymer.
 41. The silanecopolymer of claim 28, wherein the one or more polyisocyanates comprisedicyclohexylmethane-4,4′-diisocyanate (HMDI), the organo-functionalsilanes comprise N-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane,and the molecule having at least two functional groups, which may be thesame or different, that are reactive with isocyanate is a polyethyleneglycol having a weight average molecular weight of about
 1450. 42. Thesilane copolymer of claim 28, wherein the polymer has a coefficient offriction when wet of between 0.01 and 0.2.
 43. The silane copolymer ofclaim 28, wherein the polymer has a coefficient of friction when wet ofbetween 0.01 and 0.12.
 44. The silane copolymer of claim 28, wherein thepolymer has a coefficient of friction when wet of between 0.01 and 0.06.45. The silane copolymer of claim 28, wherein the molecule having atleast two functional groups, which may be the same or different, thatare reactive with an isocyanate functional group, has at least two aminofunctional groups.
 46. A process comprising reacting molecules with eachother to form a polymer, wherein the molecules consist essentially of:one or more polyisocyanates; a polymer having at least two functionalgroups, which may be the same or different, that are reactive with anisocyanate functional group; and, one or more organo-functional silaneshaving at least two functional groups, which may be the same ordifferent, that are reactive with an isocyanate functional group, andhaving at least one functional group reactive with a silicone rubbersubstrate.
 47. The process of claim 46, further comprising combining themolecules with a solvent.
 48. The process of claim 46, furthercomprising the addition of a catalyst that is catalytic for the reactionbetween an isocyanate and a molecule having at least two functionalgroups, which may be the same or different, that are reactive withisocyanate.
 49. The process of claim 46, wherein the catalyst isselected from the group consisting of N,N-dimethylaminoethanol,N,N-dimethyl-cyclohexamine-bis(2-dimethyl aminoethyl) ether,N-ethylmorpholine, N,N,N′,N′,N″-pentamethyl-diethylene-triamine,1-2(hydroxypropyl) imidazole, stannous octoate, dibutyl tin dilaurate,dioctyltin dilaurate, dibutyl tin mercaptide, ferric acetylacetonate,lead octoate, and dibutyl tin diricinoleate.
 50. The process of claim46, wherein the molecules having at least two functional groups, whichmay be the same or different, that are reactive with an isocyanatefunctional group comprise a diol.
 51. The process of claim 46, whereinthe molecules having at least two functional groups, which may be thesame or different, that are reactive with isocyanate is a poly(ethyleneadipate), a poly(diethyleneglycol adipate), a polycaprolactone diol, apolycaprolactone-polyadipate copolymer diol, apoly(ethylene-terephthalate)diol, a polycarbonate diol, apolytetramethylene ether glycol, a polyethylene glycol, an ethyleneoxide adduct of polyoxypropylene diol, or an ethylene oxide adduct ofpolyoxypropylene triol.
 52. The process of claim 50, wherein the diol isa polyethylene glycol.
 53. The process of claim 52, wherein thepolyethylene glycol has a weight average molecular weight ofapproximately
 1450. 54. The process of claim 52, wherein thepolyethylene glycol has a weight average molecular weight ofapproximately
 8000. 55. The process of claim 46, wherein the one or morepolyisocyanates comprise a diisocyanate.
 56. The process of claim 55,wherein the diisocyanate is selected from 4,4′-diphenylmethanediisocyanate and position isomers thereof, 2,4- and 2,6-toluenediisocyanate (TDI) and position isomers thereof, 3,4-dichlorophenyldiisocyanate, dicyclohexylmethane-4,4′-diisocyanate (HMDI),4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylene diisocyanate(HDI) and position isomers thereof, isophorone diisocyanate (IPDI), andadducts of diisocyanates.
 57. The process of claim 55, wherein thediisocyanate is dicyclohexylmethane-4,4′-diisocyanate (HMDI).
 58. Theprocess of claim 46, wherein the one or more organo-functional silanescomprise an amino-functional alkoxysilane.
 59. The process of claim 58,wherein the amino-functional alkoxysilane isN-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane.
 60. The processof claim 46, wherein the molecule having at least two functional groups,which may be the same or different, that are reactive with an isocyanatefunctional group has at least two amine functional groups.
 61. Theprocess of claim 46, wherein reacting molecules with each other to forma polymer comprises: (a) reacting the molecules having at least twofunctional groups, which may be the same or different, that are reactivewith isocyanate with an excess of the one or more polyisocyanates in thepresence of a catalyst to form a polyurethane-urea prepolymer havingterminal isocyanate groups; and (b) reacting the prepolymer formed in(a) with one or more organo-functional silanes having at least twofunctional groups, which may be the same or different, that are reactivewith the isocyanate groups on the polyurethane-urea prepolymer andhaving at least one functional group reactive with a silicone rubbersubstrate to form a silane copolymer.
 62. The process of claim 61wherein (b) occurs in the presence of a solvent.
 63. The process ofclaim 46, wherein reacting molecules with each other to form a polymercomprises: (a) reacting the one or more organo-functional silanes havingat least two functional groups, which may be the same or different, thatare reactive with an isocyanate functional group and having at least onefunctional group reactive with a silicone rubber substrate with anexcess of the one or more polyisocyanates to form a polyurea prepolymerhaving terminal isocyanate groups; and, (b) reacting the polyureaprepolymer formed in (a) with the one or more molecules having at leasttwo functional groups, which may be the same or different, that arereactive with isocyanate in the presence of a catalyst to form thesilane copolymer.
 64. The process of claim 63, wherein step (a) occursin the presence of a solvent.
 65. The process of claim 61, wherein theprocess further comprises stabilizing the copolymer formed in (b) bytreating the copolymer with an alcohol.
 66. The process of claim 63,wherein the process further comprises stabilizing the copolymer formedin (b) by treating the copolymer with an alcohol.
 67. A coatingcomprising a silane copolymer wherein the copolymer is the reactionproduct of: i) one or more molecules having at least two functionalgroups, which may be the same or different, that are reactive withisocyanate; ii) one or more organo-functional silanes having at leasttwo functional groups that are reactive with an isocyanate group and atleast one functional group reactive with a silicone rubber substrate;and, iii) one or more polyisocyanates.
 68. The coating of claim 67,wherein the coating comprises: a primer coat comprising the silanecopolymer; and, a top coat that overlays at least a portion of theprimer coat.
 69. The coating of claim 68, wherein the top coat is thecombination of a polyethylene oxide and a reactive mixture ofpolyfunctional isocyanate and polyol.
 70. The coating of claim 68,wherein the top coat is the reaction product of molecules comprising:one or more polyisocyanates; one or more organo-functional silaneshaving at least two functional groups, which may be the same ordifferent, that are reactive with isocyanate and at least one functionalgroup reactive with a silicone rubber substrate; and one or morepolyethylene glycols.
 71. The coating of claim 67, wherein the coatinghas a coefficient of friction when wet of between 0.01 and 0.2.
 72. Thecoating of claim 67, wherein the coating has a coefficient of frictionwhen wet of between 0.01 and 0.12.
 73. The coating of claim 67, whereinthe coating has a coefficient of friction when wet of between 0.01 and0.06.
 74. The coating of claim 67, wherein the molecule having at leasttwo functional groups, which may be the same or different, that arereactive with an isocyanate functional group, has at least two aminofunctional groups.
 75. The coating of claim 67, wherein the moleculeshaving at least two functional groups, which may be the same ordifferent, that are reactive with an isocyanate functional groupcomprise a diol.
 76. The coating of claim 67, wherein the moleculeshaving at least two functional groups, which may be the same ordifferent, that are reactive with isocyanate are selected from apoly(ethylene adipate), a poly(diethyleneglycol adipate), apolycaprolactone diol, a polycaprolactone-polyadipate copolymer diol, apoly(ethylene-terephthalate)diol, a polycarbonate diol, apolytetramethylene ether glycol, a polyethylene glycol, an ethyleneoxide adduct of polyoxypropylene diol, or an ethylene oxide adduct ofpolyoxypropylene triol.
 77. The coating of claim 75, wherein the diol isa polyethylene glycol.
 78. The coating of claim 77, wherein thepolyethylene glycol has a weight average molecular weight ofapproximately
 1450. 79. The coating of claim 77, wherein thepolyethylene glycol has a weight average molecular weight ofapproximately
 8000. 80. The coating of claim 67, wherein the one or morepolyisocyanates comprise a diisocyanate.
 81. The coating of claim 80,wherein the diisocyanate is seleeted from 4,4′-diphenylmethanediisocyanate and position isomers thereof, 2,4- and 2,6-toluenediisocyanate (TDI) and position isomers thereof, 3,4-dichlorophenyldiisocyanate, dicyclohexylmethane-4,4′-diisocyanate (HMDI),4,4′-diphenylmethane diisocyanate (MDI), 1,6-hexamethylene diisocyanate(HDI) and position isomers thereof, isophorone diisocyanate (IPDI), andadducts of diisocyanates.
 82. The coating of claim 80, wherein thediisocyanate is dicyclohexylmethane-4,4′-diisocyanate (HMDI).
 83. Thecoating of claim 67, wherein the one or more organo-functional silanescomprise an amino-functional alkoxysilane.
 84. The coating of claim 83,wherein the amino-functional alkoxysilane isN-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane.
 85. The coatingof claim 67, wherein the one or more polyisocyanates comprisedicyclohexylmethane-4,4′-diisocyanate (HMDI), the organo-functionalsilanes comprise N-(2-aminoethyl)-3-aminopropyl-methyldimethoxy silane,and the molecules having at least two functional groups, which may bethe same or different, that are reactive with isocyanate is apolyethylene glycol having a weight average molecular weight ofapproximately
 1450. 86. The coating of claim 67, wherein the moleculehaving at least two functional groups, which may be the same ordifferent, that are reactive with an isocyanate functional group has atleast two amine functional groups.
 87. The coating of claim 67, whereinthe coating further comprises a hydrophilic polymer.
 88. The coating ofclaim 87, wherein the hydrophilic polymer is a polysaccharide,hyaluronic acid or a salt or a derivative thereof, sodium alginate,chondroitin sulfate, a cellulose, chitin, chitosan, agarose, a xanthan,dermatan sulfate, keratin sulfate, emulsan, gellan, curdlan, amylose,carrageenan, amylopectin, a dextran, glycogen, starch, heparin sulfate,a limit dextrin or a fragment thereof or a synthetic hydrophilicpolymer.
 89. The coating of claim 87, wherein the hydrophilic polymer ispolyethylene oxide (PEO), polyethylene glycol (PEG), poly(vinyl alcohol)or poly(N-vinyl) pyrrolidone (PVP).
 90. The coating of claim 68, whereinthe top coat comprises polyvinyl pyrrolidone and a reactive mixture of apolyfunctional isocyanate and a polyol.
 91. The coating of claim 70,wherein the polyethylene glycol used to form the top coat has a weightaverage molecular weight of about 8000.